1. Field of the Invention
The invention relates to a mechanism for providing and adjusting rotational resistance in a spool and more particularly to a welding wire dispensing assembly and apparatus for retarding the rotation of a filler wire spool used to feed filler material to a welding torch such as an arc welding head or gun.
2. Description of the Related Art
In certain welding processes, a filler material, in the form of a coiled wire, such as steel or aluminum wire, is fed to a welding machine such as an arc welding gun. The wire filler material is typically fed to the welding site by motor driven rollers carried by the welding gun or by rollers mounted in a remote cabinet or both. During this feeding process, the level of tension on the wire should be regulated as the level of tension on the wire affects the column strength of the wire. Typically, a frictional drag force is applied to the wire spool in order to create the proper amount of rotational resistance in the spool and the proper amount of tension in the wire. Typically, the frictional drag force is created (1) between a spindle, rotatably mounted with the spool and a stationary axle member or (2) between a spring biased torsion arm and a rim of the spool.
In welding wire support assemblies, the degree of frictional drag provided must frequently be adjusted. Welding wire support assemblies typically may hold wires made of one of many types of material, including steel, aluminum, and other materials. These materials have differing densities and, as such, have differing levels of inertia. Thus, for different wires, the rotational resistance needed to create the proper tension in the wire may be different.
Typically, in devices relying on creating a frictional drag force, the frictional drag force is increased or decreased by rotating a nut about a bolt. In this way, more or less pressure is applied to a frictional pad such as a fabric washer. This prior art is inaccurate and inconsistent, because there exists no easily calculable method for determining when the appropriate setting has been achieved. Furthermore, methods for operating this prior art allow for too much operator error. Many operators adjust rotational resistance by sight, and rely on a trial and error method if their first estimate is incorrect. Other operators rotate the nut until it is as tight as possible, and then rotate the nut in the opposite direction a specified number of rotations based on the type of wire on the spool. For example, an operator may rotate the nut three rotations for one type of wire and five rotations for another type of wire. This method is subject to operator error and produces unpredictable and inaccurate results because no mechanism exists to indicate when the correct adjustment level is achieved.